harnden



5 Sheets-Sheet 1 Jr"; verv t or-:

John [2 HarndenJr;

His Attorney Nov. 22, 1960 J. D. HARNDEN, JR

IGNITION- SYSTEM Filed Dec. 27, 1957 1T in Nov. 22, 1960 J. D. HARNDEN,JR 2,961,580

IGNITION SYSTEM Filed Dec. 27, 1957 I 3 Sheets-Sheet 2 2a 0 F 34 g :EHE

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Inventor": John D. Har-nder7,Jr; 139% 18% His Attorney.

Nov. 22, 1960 Filed Dec. 27, 1957 J. D. HARNDEN, JR 2,961,580

IGNITION SYSTEM 3 Sheets-Sheet 3 Inventor-.- Johrv D- Ha/"n der7,Jr;

tag m 2M H/ls A tic/"r7 e .current source to the spark plugs.

wtm nite IGNITION SYSTEM Filed Dec. 27, 1957, Ser. No. 705,551

14 Claims. (Cl. 315254) This invention relates to an ignition system forinternal combustion processes and, more particularly, to an ignitionsystem utilizing a pulse generator for producing ignition impulsesconstructed from saturable impedance devices.

One of the objects of my invention is to provide an ignition systemwhich eliminates the use of mechanical breaker point assemblies.Conventional ignition systems as utilized in todays internal combustionengines comprise a spark coil having a low voltage primary energizedfrom a unidirectional source, such as the car battery, and a highvoltage secondary connected through the mechanical distributor to thespark plugs. The high voltage ignition impulses for breaking down thespark gap in the plugs are produced by a breaker assembly connected inthe primary of a spark coil. This breaker assembly is actuatedperiodically to interrupt the circuit, thereby producing rapid change influx in the spark coil and inducing high voltage impulses in thesecondary of the coil.

Such ignition systems leave much to be desired from the standpoint ofeffectiveness, reliability and efficiency.

It is quite clear that the current interrupting breaker points place aninherent limitation upon the entire system, since these points mustcarry the entire primary current for firing the cylinders in the engine,causing severe wear and ultimate destruction of breaker point surfaces.In addition to the necessary periodic replacement of the points, acontinuous deterioration of engine performance results, since therapidity with which the primary circuit can be interrupted andconsequently the sharpness of the impulses decreases as the breakerpoint surfaces are destroyed. Because of the degeneration of theseimpulses, proper ignition is hindered, resulting in poor engineperformance and increased fuel consumption.

Furthermore, conventional ignition systems are inherently inefiicient,since a major portion of the system power is dissipated across thebreaker points rather than in the spark discharge.

Modern engine design leading towards increased horsepower andcompression ratios intensify all of the problems resulting from the useof mechanical interrupting means since higher power levels at the sparkdischarge gaps are required and thus the breaker points must interrupthigher currents accelerating the destruction of the breaker pointsurfaces. A limit has thus been reached in the application of presentlyavailable ignition systems and an entire new approach and philosophy isrequired.

One solution to this problem, disclosed in patent specification SerialNo. 705,669 entitled Ignition Systems by E. D. Cook, filed December 27,1957, assigned to the General Electric Company, utilizes a saturablemagnetic device to release power periodically from an alternating Thesaturable magnetic device includes a direct current control Windingincorporating a breaker point assembly actuated in synchronism with theengine to control the saturation of the magnetic device. Thus, thebreaker points act as the synatent O i chronizing means in the controlwinding circuit to supply 2,961,586 Patented Nov. 22, 1%60 iceelectrical power to the spark plugs and do not interrupt the primarycurrent. Hence, the load on the breaker points is reduced with theconsequent reduction of the breaker point surface attrition. However,the elimination of the breaker points by utilizing an entirely staticmagnetic pulse generator to supply the ignition impulses is desirable.

One of the advantages of such a system is that a low power alternatingvoltage source may be utilized. Furthermore, spark advance and retardmay be achieved without utilizing mechanical movements. In addition, itis also possible to eliminate the mechanical distributor entirely.

It is another object of this invention, therefore, to provide anignition system utilizing completely static magnetic ignition pulsegenerating means.

A further object of this invention is to provide an ignition systemutilizing electrical spark advance and re tard control.

Still another object of this invention is to provide an ignition systemutilizing contactless distributing means.

Other objects and advantages of the invention will become apparent asthe description of the invention proceeds.

The above objects are achieved by means of a static saturating magneticpulse generator energized from an alternating voltage source driven fromthe engine. The self-saturating magnetic pulse generator produces asteep wave front impulse during each alternation of the voltage by thesuccessive saturation of a pair of saturable impedances.

In alternative embodiments, a multiplicity of pulse generating networksis provided for producing a multiplicity of time-displaced ignitionimpulses during each alternation of the alternating voltage, the pulsesfrom the individual networks being coupled to dilferent ones of theengine spark plugs, eliminating the mechanical distributor.

The novel features which are believed to be characteristic of thisinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and method ofoperation together with further objects and advantages thereof may bestbe understood by reference to the following description taken inconnection with the accompanying drawing in which:

Figure l is a schematic diagram of one embodiment of the invention;

Figures Za-Zb are waveforms useful in illustrating the operation of thecircuit of Figure 1;

Figure 3 is a graph illustrating an idealized rectangular hysteresisloop useful in explaining the operation of the saturable devices ofFigure 1;

Figure 4 is a schematic diagram of an alternative embodiment of theinvention utilizing contactless distribution;

Figures 5a-5e are waveforms useful in illustrating the operation of thecircuit of Figure 4;

Figure 6 is yet another embodiment of the invention; and

Figures 7a-7e are waveforms useful in illustrating the operation of thecircuits shown in Figure 6.

Referring now to Figure 1, the ignition system includes an alternatingvoltage source driven by the engine and a pair of saturable magneticdevices adapted to saturate at different times during each voltagealternation to produce an ignition impulse during each alternation.Thus, a source of alternating voltage 1, such as a tachometer generatoror the like, is driven by the internal combustion engine 2 through themedium of the timing shaft 3, such as the camshaft which operates infixed time relation to the movement of the reciprocating engineelements, to produce an output voltage, the frequency of which isproportional to the engine speed. Coupled to the generator 1 is a staticmagnetic pulse generator 4 comprising a saturable reactor 5 and asaturable transformer 6, the primary winding 7 of which .is connected inseries with the reactor 5 across the generator'terminals. A high leakageresistance 9 is connected between a .point on the saturable reactor 5and one terminal of the voltage source 1 to provide a path for a portionof the reactor 5 exciting current. The saturable devices 5 and .6 are soconstructed that they saturate during different points during .eachvoltage alternation to produce the ignition impulse. The secondary highvoltage Winding 8 of the saturable transformer 6 has one end thereofconnected to ground and the other end to a distributor 10 to distributeignition impulses through distributor contacts 11 sequentially to theappropriate spark plugs 12 of the internal combustion engine.

The saturable devices of pulse generator 4 have'their cores formed ofrectangular hysteresis loop material. Such material, as is Well known tothose skilled in the art, has a sharp transition point betweenconditions of saturation and non-saturation, so that their impedance canchange almost instantaneously from a high value to substantially zero;an idealized hysteresis characteristic of this type being illustrated inFigure 3. Reactor 5 acts essentially as a hold-ofI' reactor so that, inits unsaturated condition, substantially all of the voltage appearsacross it, blocking voltage from the saturable transformer 6. However,reactor 5 saturates at time t during each alternation with its impedancedropping substantially to zero, supplying full voltage across theprimary Winding 7 of transformer 6. However, the saturable transformer 6saturates soon after at a time t so that voltage is coupled into thesecondary and through the distributor to the respective spark plugsduring the interval t to t To compehend the operation of the pulsegenerator 4 of Figure 1 completely, it would be well to examine theunderlying theoretical considerations governing the operation ofsaturable impedance devices such as 5 and 6. The flux change ininductors such as 5 and 6 is, as is well known, proportional to thevoltage time integral of the inductive component and is defined by theequation:

Gdt

where B=flux density/ sq. unit of area. =cro'ss sectional area of coreof the inductor.

,Thus, the volt integralequationcan be rewritten toread:

:It is obvious from the above equation that the time required forsaturation may be varied by varying any one ofthe factors defined :inthe above equations. However, once all of -the parameters for a giveninductor are'settled; i.e., N, A, 'K,'the volt seconds fed: arefixedlfor that particular :saturabledevice.

Keeping this .in mind, the. operation of the ignition system of Figure 1maybest be understood .byireferenc'e to Figures 2a and 2b. Initially,both the saturable reactor .:5 and :saturable :transformer a6areunsaturated; however, the impedance of'thereactor 5 ssuchthatsubstantially reactors saturate. vance required, one effectiveapproach is to utilize a all of the voltage during the illustratedpositive alternation appears across the reactor 5 as 2 shown in Figure2a, and none across winding7. At time t determined by its parameters,the necessary volt-seconds, illustrated by means of the shaded portion,cause the reactor 5 to saturate and its impedance drops substantially tozero. Therefore, after t substantially all of the generator voltageappears across the primary 7 of the saturable transformer 6 as thevoltage e However, the parameters of the saturable reactor 6 are suchthat it holds off only a very small volt-second area and shortly after,at time t it saturates, its impedance dropping substantially to zero,removing voltage across the secondary =8 terminating the ignitionimpulse. At time t the core has returned to +3 and is in condition totraverse the reverse side of the loop during the negative alternation.

During the negative alternation the same reactor saturation sequenceoccurs producing a negative impulse. Thus, an ignition impulse isproduced during each alternation of the voltage produced by the voltagegenerator '1 with successive pulses having opposite polarities.

After t until the end of each alternation at the current is limited onlyby the circuit resistances of the saturable reactors 5 and 6. Althoughthis value of resistance is small, overheating Will not result since thetachometer generator 1 utilized as the alternating voltage supply forthe circuit contains reactance which limits the current flow. .Leakageresistance 9 is of very high value and, ashas been pointed outpreviously, merely provides a path for the exciting current of thesaturable reactor 5.

From an examination of Figure 2a it becomes apparent that such anignition system requires a generator having a small power output becausethe average power requirement is low and the efliciency is high. Duringtheinterval t t essentially the only current flowing is the smallexciting current reactor 5, determined by the coercive force Hillustrated in Figure 3, so that the power dissipation is negligible.Similarly, .from T T substantially all the power goes into spark energy,less small copper and core losses. This is in striking contrast topresent day ignition systems Where approximately twice as much power isdissipated in the system as is delivered to spark plugs.

It is apparentin considering the ignition system of-Fi-gure 1 thatchanges in engine speed affect the outputfrequency of the tachometergenerator 1 since it .is driven from the engine cam shaft 3. Figure 2billustrates the relationship between the alternating voltage output ofthe generator 1 for different engine speeds. The solid curve erepresents the generator output for one speed and broken curve 2 thatfor a higher speed. Itis clear that the time z 'and t when reactors 5and 6 saturate for voltage e occursearlier than t and t for'the voltageincreases and hencethe volt-seconds to saturate the reactors areachieved earlier in time, preserving the electrical firing angle. Thatis, although thepulses a anda occur at different times they occur.at-the; same position .in electrical degrees of their respectivevoltages e and. e

In describing the functioning of pulse .generator l with reference toFigure 2b for various engine :speeds .and

' generator frequencies, it was assumed, for simplicityo'f explanation,that the ignition impulses are produced .with their electrical firingangle preserved. However, in actuality, as enginespeed varies it isnecessary to provide steady state spark advance or retard withvariations in engine speed toinsure proper operation. This is achievedby varying the point in electrical degrees at which the For the smallamount of spark 'adtachometer the output of which has a linear voltagevs.

frequency characteristic. The output voltage is connected to a biaswinding having a capacitor connected in series therewith which thusprovides a frequency sensitive circuit element having high impedance atlow and low impedance at high frequencies. The bias winding is wound onthe core of the reactor and provide a bias varying with frequency andthus speed, producing saturation earlier in the alternation (in advanceof t with increasing speed.

Another approach contemplates using control and bias windings with thesaturable reactor 5 that are energized from the tachometer generatorvoltage, the magnitude of which is varied by a potentiometer arrangementunderstood to be both static and contact in response to the enginethrottle movement to compensate for transient advances.

Yet a third alternative for controlling the advance or retard of thespark is to use a saturable reactor element 5 of the variac type havinga variable number of turns which may be selectively changed to controlthe voltseconds necessary for saturation. In this manner the electricalangle of the pulse may be advanced or retarded selectively from thethrottle mechanism of the engine.

In addition it is, of course, possible to change the position of thetachometer generator stator directly from throttle with changes in speedto maintain spark control in a manner analogous to that utilized tocontrol breaker point advance in present day ignition systems.

All of these various methods of controlling the spark conditions havebeen described, to illustrate briefly, the various techniques that maybe utilized to enhance performance.

The output frequency per camshaft revolution of the tachometer generator1 of Figure 1 is, of course, determined by the number of cylinders inthe engine. That is, for example, in most six or eight cylinder enginesit takes two camshaft revolutions to fire all the spark plugs in theengine. Since the pulse generator 4 produces two output pulses for eachcycle of the alternating voltage, it becomes obvious that theconstruction of the tachometer generator and the relationship of theoutput frequency to each camshaft revolution is determined from thesevarious parameters to produce an adequate number of ignition impulses tofire the engine.

In the ignition system illustrated in Figure 1, a single magnetic pulsegenerator is utilzed to produce a series of ignition impulses, whcih areapplied to selected ones of the engine spark plugs by means of amechanical distributor driven from the camshaft. Such a mechanicaldistributor means is subject to surface attrition of the distributorpoint since a mechanical wiper and contact arrangement transmits theignition impulses. It is desirable, in order to achieve the utmost inreliability, to eliminate the mechanical distributor and Figure 4illustrates an embodiment of such an ignition system. A multiplicity ofpulse-generating networks of the type illustrated in Figure 1 arecoupled to a source of alternating voltage driven from the engine. Eachof the (n) individual pulse generating networks are directly andpermanently coupled to one of the engine spark plugs.

An alternating voltage source, such as a tachometer generator 1, isdriven from the engine 2 by means of a camshaft 3 and has a pair ofoutput terminals, one of which is grounded. The output voltage from thetachometer generator 1 i coupled to a multiplicity of pulsegeneratingnetworks 2% 21, 22 and 23, connected in parallel across the generatorterminals. The respective networks include saturabl-e hold-off reactors24, 25, 26 and 27, and saturable transformers 28, 29, 30 and 31 having,respectively, primary windings 28a, 29a, 3% and 31a, and secondary highvoltage windings 28b, 29b, 3%, and 3112. Each of the saturable hold-offreactors is connected in series with the primary winding of itsrespective saturable transformer across the output terminals of thetachometer generator 1. Thus, each of the pulse generating networks 20,21, etc., produces an output pulse during each alternation of thevoltage from the generator 1. Each of the secondary windings 28b, 2%,etc. are grounded at one end and connected at the other to an individualone of the spark plugs 32. In this manner the output from the individualpulse generating means is continuously connected to a given one of theengine spark plugs 32.

To achieve the proper spark plug firing sequence it is, of course,necessary that the output pulse produced by the individual pulsegenerators be displaced in time. To this end the individual hold-offreactors 24, 25, etc. of each of the pulse generating networks has adifferent voltsecond characteristic and, as a consequence, saturates atdifferent points during each voltage alternation. This may be seen mostclearly with reference to Figures Sa-Se. FigureSa illustrates thecharacteristics of the pulse generator 2i) and, as can be seen there,its hold-off reactor 24 has a volt-second characteristic such that itsaturates at time 23 to produce the pulse c1 In Figure 5b, representingthe operation of pulse generator 21, the hold-off reactor 25 of thisnetwork is such that its volt-second characteristic causes it tosaturate at time b to produce a time displaced output pulse a In asimilar fashion, Figures 50 and 5d illustrate the characteristics of theremaining networks 22 and 23 which are so constructed as to produce thetime displaced pulses (1 and i2 As a consequence, a pulse train a 0etc., such as is illustrated in Figure Se, is produced during eachvoltage alternation from the tachometer generator 1 which pulses aredirectly coupled to one of the spark plugs.

For the sake of simplicity, the ignition system of Figure 4 has beenillustrated as a four cylinder engine. It is obvious, of course, thatthis system is clearly applicable to engines of six or eight cylinderengines or, in fact, engines having any number of cylinders. Fourcylinders were illustrated in order to simplify the drawing byminimizing the number of circuits shown; but it is apparent that pulsetrains having any number of pulses may be produced by utilizing separatepulse-forming networks having different volt-second characteristics,eliminating the necessity for a mechanical distributor and thus greatlyimproving the reliability of the ignition system.

As can be seen from Figures 5a5e, the individual pulses of the pulsetrain vary in amplitude depending on the position during eachalternation at which they occur. It is obvious, of course, that themagnitude of the smallest pulse in the train must be sufficiently highto cause a breakdown of the gap of its individual spark plug. Hence, theminimum condition as far as sparking voltage is established by thesmallest amplitude pulse in the pulse train.

In the ignition system of Figure 4 a multiplicity of networks, eachhaving different saturation characteristics, are provided to generatethe individual pulses of the train. However, it may be much moredesirable in certain circumstances to utilize identical networks toavoid having to produce and utilize so many different ones. Figure 6illustrates an alternative embodiment of the ignition system of Figure 4wherein a multiplicity (n) of networks having the same saturationcharacteristics are provided which networks have applied thereto one ofa multiplicity (n) of phase displaced alternating voltages to generatethe required pulse train.

A multiphase alternating voltage source 41 such as a tachometergenerator produces a multiplicity of phase displaced alternatingvoltages and is driven from an internal combustion engine 2 by means ofthe familiar camshaft 3. The tachometer generator 41 is of the permanentmagnet type, having a permanent magnet rotor 42 mounted on the camshaft,and n-spaced armature winding pairs 43, 44, 45 and 46 positioned aroundthe periphery of the rotor so that nphase displaced voltages are inducedtherein by each rotation of the permanent magnet rotor 42. Each of thearmature windings 43, 44,

7 etc. illustrated as a single coil for the sake of simplicity, of course,.comprises a pair of coils. Since the individual armature windingsare displaced in space about the periphery of the permanent magnetrotor, the voltages induced in the respective windings are phasedisplaced as illustrated in Figures 7a7d. Each of the armature windings43, 44, etc. is connected to an individual one of :2- pulse generatingnetworks '47, 43, 49 and 5t). Each of thesepulse networks includesaturable hold-off reactors '51, '53, '54, and '55 and saturabletransformers 56, 57, 58 and 59 .having, respectively, primary windings56a, 5741,5841 and 59a, and high voltage secondary windings 56b, 57b,58b and 59b. The individual saturable holdofi reactors 51, etc. of theindividual pulse networks are connected in series with the primarywindings 56a, etc. of the saturable transformers across the armaturewindings 46, etc. 'Each network thus has applied thereto one of'thephasedisplaced voltages from the generator 41.

The hold-oh" reactors 51, etc. of each network have identicalvolt-second characteristics whereby they saturateat the same pointduring each alternation. How- .ever, as the applied alternating voltagesare phase displaced, each of these networks produce an output pulsedisplaced in time by a similar amount. Hence, as can be seenin Figure7e, a multiplicity of output pulses (1 a 11 and Q are produced which areapplied to individual ones of the spark plugs 60 through therespectiVesecondary windings 56b, 57b, etc. of the individualtransformers.

.Theignition system of Figure 6 thus provides ignition impulses to theindividual spark plugs of an internal combustion engine withoututilizinga mechanical distributor system, achieving the utmost in reliability byeliminating allmechanical parts.

Once more, for thesake of simplicity of explanation and illustration, afour cylinder engine has been illustrated but it is obvious, of course,that the ignition system embodying applicants invention may be utilizedwith internal combustion engines of any number of cylinders.

In describing the apparatus of Figure 6, a tachometer generatorhas beenutilized which has a multiplicity of spaced armature windings to producethe desired number of phase displaced voltages. It will be apparent thatthe tachometer generator of Figure 6 may be replaced by a'number ofsingle-phase tachometers having permanent-magnetrotors which may bepositioned on the camshaft with the individual rotors so positionedrelative to each other that the proper phase relation among theirvoltages is achieved.

'From the previous description, it can be seen that an ignition systemhas been provided which utilizes no mechanical breaker points to producethe sparking voltage and which, is alternative embodiments, eliminatesthe need-for mechanical distribution means. Thus, an ignition system ofhigh accuracy, reliability, and efficiency has been provided.

;It:is apparent that the concept of this invention is not limitedtointernal combustion engines but may be used wherever electricaldetonation is required such as, for example, toil burner ignitionsystems.

One of the very-important advantages accruing is the inherent accuracyand stability of this system which eliminates the need for periodadjustment and renewal of timing circuit componentssuch points, cams,etc., due to mechanical and electrical wear and failures.

In addition, by virtue of using an independent energy source; 'i.e., theengine driven generator, the system is not directly dependent on batteryconditions resulting "from numerous extraneousfactors such as age,weather, prior history, etc.

'While a particular embodiment of this invention has i'heen :showniitwill, of course, be understood that it rs 1 not limited thereto sincemany modifications both .in

the circuit arrangements and in the instrumentalities employed may bemade. It is contemplated by the appended claims to cover any suchmodifications as fall within the truespirit and-scope of this invention.

What I claim as new and desire to secure by Letters Patent of theUnited'States is:

1. In an engine ignition system, the combination comprising analternating voltage generator driven from said engine, a completelystatic pulse generating means coupled to and continuously energized fromsaid generator, said static pulse generating means including a hold offsaturable impedance means adapted to block the voltage from saidgenerator until it saturates at a given point during each voltagealternation whereby steep fronted ignition impulses are produced duringeach alternation.

2. "In an engine ignition system, the combination comprisinganalternating voltage generator driven from said engine, a magneticpulsegenerating means coupled to said generator including a pair ofsaturableimpedance means adapted to saturate at different points during eachvoltage alternation whereby steep fronted ignition impulses are producedacross one of the saturable means during each alternation, and meanscoupled to said one of said saturable means to apply successive ones ofsaid pulses to'selected engine spark plugs.

3. In an engine ignition system, the combination comprising analternating voltage generator driven from said engine, a magneticpulsegenerating means coupled to said generator including a pair ofseries connected self-saturating impedance means adapted to saturate atdifferent times during eachvoltage alternation whereby ignition impulsesare produced across that impedance which saturates at the later timeduring each alternation, and means coupled to said last named impedanceto apply said impulses to selected engine spark plugs.

4. In an engine ignition system, the combination comprising analternating voltage generator drivenfrom said engine, a magnetic pulsegenerating means coupled to said generator including a self-saturatingimpedance means, a self-saturating transformer means having a primaryand secondary windings the primary winding of which is connected inseries with said impedance means across said generator, said impedancemeans having a higher impedance and saturating earlier than saidtransformer means during each alternation whereby substantially all ofsaidvoltage appears across said impedance during its unsaturatedcondition and across said transformer during its saturated conditioninitiating a sharp pulse wave front upon saturation of said impedancemeans and terminating said pulse upon saturation of said transformer,and means coupled to the secondary winding of said transformer todistribute said pulses to engine spark plugs.

'5. In an engine ignition system, the combination comprising analternating voltage generator driven from said engine, ,a magnetic pulsegenerating means coupled to said generator including a hold-oh saturableimpedance having an impedance in its unsaturated condition such thatsubstantially all of the voltage from said generator appearsthereacross, a load saturable impedance having saidgenerator voltageapplied thereto upon saturation of said hold-oil reactor to produce thefront edge of an ignition impulse and producing'the'ba'ck edge of theignition impulse when it saturates, and means coupled to said loadimpedance to apply said impulses to the engine spark plugs.

6. Inan engine ignition system, the combination comprising analternating voltage generator driven from said engine, magnetic pulsegenerating means coupled'to said generator including a multiplicity ofpulse forming means each adapted to produce a pulse during eachalternation of said voltage, said pulse-forming means comp-rising atleast one saturable impedancermeans adapted to saturate at given-pointsduring each voltage alternation, and means coupled to each; of saidpulse-forming means to apply the pulses-therefrom to a selected one ofthe engine spark plugs.

7. In an engine ignition system, the combination comprising analternating voltage generator driven from said engine, magnetic pulsegenerating means coupled to said generator including a multiplicity ofpulse forming means each adapted to produce a pulse during eachalternation of said voltage, said pulse forming means comprising ahold-off saturable impedance and a load saturable impedance, saidhold-oil impedance in its unsaturated condition holding said voltage oilfrom said load impedance and transferring said voltage thereto uponsaturation to produce pulses across said load impedance, and meanscoupled to the load impedances of each of said pulse forming means todistribute the pulses therefrom to a selected one of said engine sparkplugs.

8. An engine ignition system according to claim 7 wherein the saturableload impedances are saturable transformers the primary winding of eachbeing connected in series with its respective hold-off impedance and thesecondary winding of each adapted to supply the pulses to one of theengine spark plugs.

9. In an engine ignition system, the combination comprising analternating voltage generator driven from said engine, magentic pulsegenerating means coupled to said generator including a multiplicity ofpulse forming means each adapted to produce a pulse during eachalternation of said voltage, each of said pulse forming means producinga pulse during each voltage alternation which pulse is displaced in timerelative to each of those produced by the remaining pulse forming means,and means coupled to each of said pulse forming means to apply thepulses therefrom to one of the engine spark plugs.

10. In an engine ignition system, the combination comprising analternating voltage generator driven from said engine, magnetic pulsegenerating means coupled to said generator including a multiplicity ofpulse forming means each adapted to produce a pulse driving eachalternation of said voltage, each of said pulse forming means comprisingtwo series connected saturable reactors having different volt-secondcharacteristics whereby they saturate at different times during eachvoltage alternation to produce a pulse, the saturable reactors of eachpulse forming means having volt-second characteristics which aredifferent from corresponding reactor pairs of the remaining ones wherebya pulse train is produced during each voltage alternation, and meanscoupled to each pulse forming means to distribute the pulses toindividual engine spark plugs.

11. In an engine ignition system, the combination comprising amultiphase alternating voltage generator driven by said engine producinga multiplicity of phase displaced alternating voltages, a multiplicityof pulse forming networks coupled to said generator and adapted toreceive different ones of said phase displaced alternating voltages,each of said networks containing saturable impedance means havingidentical volt-second saturation characteristics with corresponding oneof other networks whereby each network produces a pulse displaced fromthose of the remaining networks by the same number of electrical degreesas their associated phase displaced alternating voltage, and meanscoupled to each of said networks to distribute the respective pulses toone of the engine spark plugs.

12. The engine ignition system according to claim 11 wherein each ofsaid networks comprises two series connected saturable impedances havingdifferent volt-second characteristics whereby a pulse is produced ineach network during each voltage alternation.

13. The engine ignition system according to claim 12 wherein thealternating voltage generator comprises a permanent magnet rotor and nspaced armature windings having n phase displaced voltages inducedtherein, each of said armature windings being connected to one of npulse forming networks to apply one of said phase displaced voltages toeach.

14. In an engine ignition system, the combination comprising analternating voltage generator means driven from said engine to generatean alternating voltage wave in fixed time relation to the operation ofthe engine, a completely static pulse circuit coupled to andcontinuously energized from said generator including a transformercomprising a primary and secondary winding, a saturable hold offimpedance means coupled to one of the windings of said transformer toblock the generator voltage from said transformer until said impedancemeans saturates to produce steep fronted ignition impulses at a fixedtime in the period of said wave, and means coupled to said transformerto apply successive ones of said ignition impulses to selected enginespark plugs.

References Cited in the file of this patent UNITED STATES PATENTS2,212,404 Robinson Aug. 20, 1940 2,392,192 Robinson Jan. 1, 19462,456,743 Short Dec. 21, 1948 2,774,878 Jensen Dec. 18, 1956 2,791,724Ekblom et al. May 7, 1957

